The present disclosure relates to advanced anode materials to permit the use of direct (i.e., unreformed) hydrocarbons as a fuel for a solid oxide fuel cell (SOFC). More specifically, the present disclosure relates to a molten metal anode (MMA)-based SOFC (MMA-SOFC) that can be used for transportation auxiliary power units (APUs).
APUs are useful as a way to provide supplemental power in heavy-duty transportation operations. One notable example is their use on tractor-trailers and related commercial vehicles in response to increased scrutiny over excessive main engine idling during extended stopover periods. In one conventional form, the APU is configured as a small internal combustion engine (ICE) that in addition to providing heat can also supply electrical power through a suitable generator in order to operate various electrical systems within the vehicle during these extended periods where the main engine is turned off. While useful for their intended purpose, such APUs problematically consume relatively large amounts of fossil fuels. Moreover, they present maintenance issues; this latter concern is particularly problematic when they do not get repaired after a failure, in that the operator of the vehicle reverts to the old method of running the vehicle's motive power unit (i.e., main engine) at idle as a way to satisfy auxiliary power needs.
Fuel cells convert a fuel into usable energy via its electrochemical reaction rather than by its combustion. As such—and in addition to having fewer failure-prone mechanical parts—fuel cells have several environmental advantages over ICEs and related power-generating sources. Within the realm of fuel cell-based power systems, SOFCs are particularly beneficial in that they take advantage of their ability to provide direct utilization of carbon-containing fuels without the need to provide significant reformation of the fuel in ways that other fuel cell configurations—such as proton exchange membrane or polymer electrolyte membrane (in either event, PEM)—cannot.
In one form, the anode of the SOFC may be made up of a fuel-containing molten metal such that upon introduction of an oxygen-bearing reactant (for example, air) to the cell's cathode, oxygen ions created at the cathode migrate through the solid electrolyte to the molten metal and ionized fuel at the anode. One significant advantage of using a molten metal anode over its solid counterpart is that most harmful emissions (typically in the form of CO2, SO2, NOX and particulate matter) that would otherwise be vented to the ambient environment can be captured. Unfortunately, having one of the fuel cell components be in a liquid-like state has resulted in significant handling problems, especially as it relates to fuel cell configurations that may be contemplated for mobile applications.